"That's why you find a kind of metal that's resilient and light. Alloys are good for that, though they're a lot harder to get ahold of because of the work involved in making them," he replies casually.

Academy City probably has some super advanced alloy not available anywhere else in the world. Excelsior, too. He figures Donnie had picked up what he needed for his crutch at the recycling facility here in Central, but he isn't sure.